Since meso and prochiral bidentate ligands have extremities which are distinguishable by their chiralities or prochiralities, such ligands behave like unsymmetrical AB bidentates in their generation of coordination isomers. The isomers possible for cobalt(III) tris- and bis-chelates containing meso and prochiral aliphatic diamine ligands will be synthesized, separated, identified, and characterized. The bidentates employed will be meso-2,3-diaminobutane and 2-methyl-1,3-diaminopropane. Force field computer calculations and enthalpies and statistical calculations of entropies will be carried out on each isomer and the results will be compared to enthalpies and entropies determined for the equilibrated cobalt(III) diamine systems. Preliminary experiments on stereoselective reactions and intramolecular rearrangements will be carried out employing the isomeric coordination compounds prepared and characterized. Isomers of coordination compounds whose isomerism depends on the relative orientations of bidentates having rotationally nonequivalent but chemically similar extremities (meso and prochiral), have not been previously separated and identified for octahedral systems. These studies will add to and expand our knowledge of stereoisomerism in coordination compounds and will provide data on some new types of isomers which can be employed in studies on stereoselective reactions and intramolecular rearrangements.